1. Field of the Invention
The invention relates to tilting and telescoping mast mechanism which may be mounted readily on the roof of a vehicle for positioning electrical devices, particularly emergency lighting fixtures, high in the air at any location that may be reached by the vehicle where use of the electrical device is desired. More particularly, the invention relates to a mast construction provided with an improved construction of seal slidably engaged between the tubular lower end of each telescoping mast section and the tubular mast section telescopically surrounding such lower end, wherein the seal construction and its mounting on the end of any tubular mast section provides a full open, obstruction-free tubular passage at the end of such mast section.
More particularly, the invention relates to a new telescoping mast construction wherein the full open, unobstructed mast section ends and passages permit circuitry wiring for control of electrical devices or fixtures mounted on the mast to pass within and through the telescopic tubular mast sections, and wherein pneumatic system air pressure is unobstructed in extending and retracting the mast.
Also, the invention relates to a tilting, telescoping mast construction wherein the mast-actuating components are housed in a housing to substantially completely protect the same from atmospheric and weather conditions which may be encountered in the operation of emergency vehicles during all seasons of the year.
2. Description of the Prior Art
The mast construction disclosed and claimed in our above-identified copending application solves problems that had been long-standing in the use of emergency vehicles having movable floodlighting equipment and other electrical devices mounted thereon. The prior art discussed therein is not relevant to the new mast construction features disclosed herein which comprise improvements in the construction and operation of the devices set forth in our said copending application.
The mast construction of the present invention incorporates a new seal device for the slidable tubular joints between telescoping mast sections, which eliminates obstructions heretofore characterizing prior telescoping masts, the mounting of seals for which obstructions have projected at least in part laterally across the lower open ends of all of the mast sections.
Elimination of such obstructions permits the tubular passages or channels through the telescoping mast sections to be used to house electrical wiring for the electrical fixtures mounted on top of the mast. Thus, retractable power cords may be located within and extended or retracted within the telescoping mast. Removal of such retractable power cords from outside of the mast is a distinct benefit because the mast protects the power cords from cord damage to which outside mounted cords may be subjected.
Futher, the outside mast location of retractable power cords in the telescoping mast construction of our above-identified copending application presents problems in connecting cords with the mast top-located electrical fixture as well as with the battery-generator power supply system of the vehicle on which the mast is mounted. The location of a power cord in the improved construction, extending in an unobstructed manner through the tubular telescoping mast sections permits the use of simple electrical plug connector devices at the top and bottom of the mast at the ends of the retractable power cord therein. A mating electrical plug connector then is used to couple the electrical fixture to the retractable power cord at the top of the mast, and similarly another mating plug is used to connect the power supply to the retractable power cord at the lower end of the mast.
As a precaution to insure unimpeded retractability of the air-pressure-actuated telescoping mast of our above-identified copending application, the pneumatic-actuating system and valving requires air pressure connections to the mast-tilting actuating cylinder at both sides of the double-acting piston. This requirement is avoided in the improved construction disclosed herein, wherein valving is simplified and an air pressure connection to the actuating cylinder at the cylinder head side of the piston is eliminated.
This pneumatic system simplification arises by locating the pivot axis on which the mast is tilted at a position laterally offset from the longitudinal axis of the mast, that is, preferably on an axis at right angles to the longitudinal axis of the mast and substantially tangential to the lower tubular end of the outer telescoping mast section. This offset location of the mast-tilting axis has been discovered to enable the mast, after the mast has retracted from extended position, to tilt by gravity on the offset axis from vertical to horizontal stored mast position. Tilting is initiated by exhausting air pressure from the mast-actuating cylinder which are pressure previously tilted the mast from horizontal position to vertical position and held the mast at such vertical position when extended telescopically.
Another difficulty encountered in use of the mast construction of our above-identified copending application involves direct exposure of some of the mast-actuating components to the elements when mounted on an emergency or other similar vehicle when traveling to and located at an area where the mast-mounted fixture is used. This difficulty is overcome with the new construction of the present invention wherein the mast-actuated components all are substantially completely protected within the mast housing.
The various described constructions and arrangements characterizing the present invention thus eliminate problems encountered in the construction and use of the telescoping mast disclosed in our above-identified copending application.